The entire submarine (or undersea) line system at least includes Submarine Line Terminal Equipment (submarine line terminal equipment, SLTE for short), Network Protection Equipment (network protection equipment, NPE for short), Power Feeding Equipment (power feeding equipment, PFE for short), a submarine repeater (submarine repeater, RPT for short), a submarine cable (Submarine cable), a submarine line Branching Unit (Branching Unit, BU for short), a submarine line Optical Equalizer (Optical Equalizer, OEQ for short), and a Submarine Line Monitor (Submarine Line Monitor, SLM for short).
The SLTE is a transmission equipment of Dense Wavelength Division Multiplexing (DWDM). The NPE is also referred as Synchronous Digital Hierarchy (SDH interconnect equipment, SDH for short) interconnect equipment (SIE), and is an interlaced connection equipment of the SDH. The PFE is installed on a land login station for powering submarine equipment. The submarine lines include optical cables and electric cables. The SLM is used for monitoring the submarine line and the positioning fault points of the submarine line. The RPT is an underwater optical amplifier equipment, which is used for amplifying a transmission signal of the SLTE, while providing a loop of an optical signal for the monitoring equipment SLM. In this regard, the RPT is for amplifying and relaying the optical signal. Since an optical signal will be attenuated or weakened in a long-distance submarine line system, it is necessary to add a repeater in the system to amplify the optical signal.
Since the RPT, the BU, and the OEQ are all underwater equipment, therefore, the underwater equipment needs to resist or withstand a high submarine (i.e., hydrostatic) pressure. In addition, it is necessary that the RPT possesses excellent electrical insulation performance against a high internal voltage of about 20 KV, while the external portion of the RPT carries out communication under the seawater.
To solve the foregoing problems, typically, a middle part of the RPT is disposed with a cylindrical body having insulation characteristics. For example, a cylindrical body of submarine cable equipment having insulation pressure-resistant cylinder body is used for providing electrical insulation to the internal portion of the cable equipment from the seawater. The cylinder body also needs to withstand the high submarine pressure, and provide sufficient installation space or clearance for the interior optical and electrical devices. Likewise, the BU and the OEQ are both also disposed with the pressure-resistant cylinder body which electrically insulates the internal portion from the seawater, while withstanding the high submarine pressure and providing sufficient installation space or clearance for the devices.
The prior art insulation and pressure-resistant cylinder body of submarine cable equipment has a three-layer structure: an outermost layer pressure-resistant cylinder for resisting the high submarine pressure, a middle insulation layer for electrically insulating the internal portion from the seawater, and an innermost layer of installation cylinder for installing the inner optical and electrical devices.
In general, the insulation material is made of an epoxy resin with fiber glass, and is disposed between the pressure-resistant cylinder (i.e., outermost layer) and the installation cylinder (innermost layer). The insulation and pressure-resistant cylinder body of submarine cable equipment is formed by: first, casting the insulation material (i.e., epoxy resin with fiber glass) on an aluminum installation cylinder (i.e., over the innermost layer). The pressure-resistant cylinder (i.e., outermost layer) is then heated to expand its radius. The insulation cast over the (aluminum) installation cylinder is pressed altogether into the heated pressure-resistant cylinder, and then followed by a cooling process. The insulation layer with the installation cylinder (i.e., the resin with fiber glass over the aluminum installation cylinder) is therefore encapsulated within the pressure-resistant cylinder.
The above process, however, exhibits a problem that the insulation layer often only achieves low installation compactness, therefore could easily sways or deform.